Actually, I think that the tiny little bit of the interrogation scene that was left in the movie makes sense from Soran's tactical point of view.

The only question we hear him ask is "tell me about trilithium". Well, he knows that Starfleet knows about Amargosa having trilithium for some reason - he overheard Data and LaForge discuss it. He himself knows he uses trilithium for killing stars in order to shepherd the Nexus. But nothing he has overheard or done would tell him whether Starfleet knows what the trilithium is for. To ask LaForge "Do you know why I need trilithium?" would be telling the officer that he does. Soran doesn't want to give information - he wants to get it. And by asking about trilithium in general, he will learn if Starfleet has put the pieces together and will follow Soran to the next point of detonation. Of course, LaForge doesn't know that Data elsewhere has done the necessary brainwork, so Soran, too, is left ill informed of Starfleet's true knowledge. But Soran still made a sensible effort to find out!